1. Field of the Technology
The present application relates to network communications involving a session initiation protocol (SIP) for virtual private networking (VPN), especially for wireless communication devices operating in wireless communication networks.
2. Description of the Related Art
In a wide area network, such as the Internet, terminals connected within it may have unsecured communications. A terminal on the Internet may gain access to a private network using virtual private networking (VPN) techniques, where a secure VPN tunnel connection between the terminal and the private network is established along with an assignment of a private IP address. The VPN negotiation may require authentication through an authentication server in the private network. The authentication may involve a typical logon procedure which includes verification of a username and password which are keyed in by the terminal. This procedure may take some time to complete.
Some communication applications utilized by the terminal, such as Voice over Internet Protocol (VoIP) applications, require the use of a session initiation protocol (SIP). SIP is well-documented in standard documents such as Request For Comments (RFC) 3261.
When the terminal needs to register with a SIP server, it sends a SIP REGISTER instruction to the SIP server. For registration, an IP address needs to be sent to the SIP server so that it can bind a SIP address to the IP address. If the terminal is on the Internet, it is initially assigned with a dynamically-assigned public IP address which will be utilized in the registration process. When a VPN connection for the terminal is subsequently established, however, the terminal will be reassigned with a new private IP address which causes the previously-registered public IP address to be obsolete. This problem is especially apparent when there are at least two SIP servers, one of which is accessible without or outside of the VPN, or at least a single SIP server which is accessible with and without a VPN.
Accordingly, there are needs for methods and apparatus for use in establishing session initiation protocol communications for virtual private networking.